1. Technical Field
The present disclosure relates to parallel mechanisms and, particularly, to a parallel mechanism used in an industrial robot and a moveable linkage of the parallel mechanism.
2. Description of Related Art
Multiple freedom parallel mechanisms, especially four freedom parallel mechanisms, are commonly used in industrial robots to provide multi-directional movement.
Referring to FIG. 4, a commonly used four freedom parallel mechanism 100 includes a stationary platform 11, a dynamic platform 12, a rotatable linkage 13 and three moveable linkages 15 connecting the stationary platform 11 and the dynamic platform 12. The rotatable linkage 13 is capable of rotating independently. The moveable linkages 15 are movable along three axes X, Y, Z. Each moveable linkage 15 includes a swing arm 151 movably connected to the stationary platform 11 and a four-link structure 152 rotatably connected to the swing arm 151. The four-link structure 152 includes four link rods 1521 connected one by one via spherical joints 153. The opposite link rods 1521 are fixed to the swing arm 151 and the dynamic platform 12 respectively. During operation, a motor or other driving device swings the swing arm 151, driving the four-link structure 152 to fold, unfold, move, or rotate, thereby realizing the three-dimensional motion of the dynamic platform 12.
However, the spherical joints 153 have a relatively limited rotation angle, about 25° or less, such that the movable distance of the four-link structure 152 is limited, thus limiting the flexibility of the common parallel mechanism 100. In addition, the spherical joints 153 are difficult to manufacture and assemble, increasing costs of the common parallel mechanism 100.
Therefore, there is room for improvement within the art.